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I'm designing a new house for myself, and I've always wanted a basement so I would have unfinished hobby space. The kind of space where you can get messy stuff on the ground like water, paint, sawdust, whatever, and nobody cares because it's just a basement.

In talking to concrete contractors, however, a full basement costs 3x as much as a slab, for only double the square footage of the main floor. In other words, I could have the same square footage for a lot less money by having a slab on grade that's twice as big, rather than putting a full basement underneath.

So, I want a "basement", but I don't care if it's actually below grade. So I was considering a design where there is just one floor on grade, and the "basement" is on the same level as the rest of the house.

By "basement", I mean a big (~800 sqft) unfinished room with a concrete (or epoxy) floor, unfinished walls, a floor drain, and everything an unfinished basement would have, just on grade level, not underneath the house. Unlike a garage, though, it would be climate controlled and not have any vehicle doors.

Are there any issues with having an unfinished room like this on the main level? Has anybody done it before? What would such a room be called? Would there be code issues, where inspectors wouldn't be able to figure out how to classify it?

Edit: Just to clarify a bit, by "unfinished", I meant not doing trim carpentry, not installing a finish floor over the concrete slab, and maybe not doing drywall if allowed by code. It would still have electrical sockets, lighting, insulation, air ducts.

Code has specific requirements based on what type of room it is. There are certain things that a "garage" requires, certain things that you can't do it a "closet", etc. I know that I don't want it to be a "garage" because "garages" have to be lower than the house for carbon monoxide, have steel doors, fire-rated drywall board, etc. "Garages" also use GFCI breakers where "bedrooms" need pricey arc-fault breakers. Bedrooms need egress windows. etc, etc.

So the essence of the question is, what should I call the room on the plans, so that it's governed by the most appropriate codes for what I'm trying to do? (My intent is to use it like an unfinished basement).

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    think about what the difference between "finished" and "unfinished" is and what that would affect. – ratchet freak Sep 15 '17 at 10:54
  • Most unfinished basements are not climate controlled. What finishing steps would you be skipping exactly? Insulation or just drywall? – statueuphemism Sep 15 '17 at 12:31
  • @mbeckish I was thinking the same thing until I saw that he wanted it climate controlled. To my knowledge, he couldn't hook into the same HVAC as the rest of the house to supply the room and classify it as a garage (fumes from potential vehicles). That said, there may be other ways to achieve climate control with localized heating and cooling and still call it a garage. – statueuphemism Sep 15 '17 at 12:37
  • Another thing to consider is property taxes in my area unfinished daylight basements are common but ranch styles with a large work room are also common in flatter areas having owned both the taxes were higher on the ranch and it was smaller than the daylight basement not sure why because the ranch was 800 feet smaller on a smaller lot in the same town so that is another thing to look into. – Ed Beal Nov 1 '17 at 13:12
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    I would call the space a workshop if any official name is needed. – wallyk Nov 21 '17 at 20:54
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The full basement may cost 3 times what the corresponding slab size may cost from a concrete perspective. But you have to also consider the cost per square foot to build the structure that covers the slab/basement. If you double your slab size you need twice as large of structure to cover it. On the other hand the structure footprint is the same size whether it has a basement or a slab under it.

  • That's true. You also save on sub-flooring and truss/joists by skipping the basement. Much of the cost of a house is in the finishing stages- garages and closets cost much less per square foot than bathrooms. I've updated the question to clarify my intent- I'm trying to figure out what the room would be called for code purposes, so I can make sure I call it the right thing, and design it to meet the correct codes. – Nick Sep 22 '17 at 19:37
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If it's on slab, it's not exactly a basement. I think what you are actually asking for is 'studio space'.

As Michael Karas, the concrete contractor is correct...the more concrete you use (ie, full basement) the more the concrete will cost. But the more slab you use, the bigger the footprint of the house, which will cost more in framing, roofing, etc.

The best of both worlds would be to make it a two story house...the first floor being mostly open studio space, second floor your living area.

But I'd strongly consider some other options as well...

  • are you building a garage? Make the garage a bit bigger for your 'hobby shop'
  • consider an out-building such as a custom shed or a pole barn
  • incorporate an extra, larger room in your house plans and just don't put much money into the finishings in it (assuming you'll eventually want to redo it when you sell the house)

what should I call the room on the plans, so that it's governed by the most appropriate codes for what I'm trying to do

This will depend entirely on your local code enforcement/planning office's preferences.

Where I live, we have to mark it as 'storage'.

But, that said...I don't know that you have to label it as anything. Code doesn't typically involve itself with finish. They may require sheetrock, but they don't care what paint you use. They may require a door, but they don't care what trim you use. They likely require a floor, but probably are fine with it being sheets of plywood.

  • I've already oversized the garage to accommodate wood working tools, but I'm also looking for some air conditioned space for working with temperature or humidity sensitive materials, like paints, epoxy, resins, etc. I also want some space to keep fish which require a stable temperature. I'm planning on going with the "incorporate an extra, larger room in your house plans and just don't put much money into the finishings in it" idea, but I don't know which codes would apply to such a room. I've updated my original question to reflect that. – Nick Sep 22 '17 at 19:41
  • And the resale point is good as well, which code set you build it under affects what you can finish and sell it as later. – Nick Sep 22 '17 at 19:42
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Generally, it needs to fall into the category of "Uninhabitable Space". You could potentially call it a storage space, a workshop, or something else clever, but those terms may ultimately get shot down by the AHJ (Authority Having Jurisdiction, such as a local building department) because if it looks and smells like it could be habitable space, they may be tempted to make you finish it anyways regardless of what you call it.

So in that case, the best recommendation I can give is to talk to the Authority Having Jurisdiction about the purpose of the room and how best to describe it in the plans. Since they will be approving the plans, they would be best able to help you come up with a term for the space that they would approve.

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